Drain pump and air conditioner with the same

ABSTRACT

A drain pump is provided that reduces the operating noise when the head is low. The drain pump has a pump casing, and an impeller. The pump casing has a drain inlet for sucking in drain water at a lower end part and a drain outlet for discharging drain water at a side part. The impeller has a shaft part extending in a vertical direction inside the pump casing, a main blade disposed on the outer circumferential side of the shaft parts, an auxiliary blade disposed on the lower side of the main blade, and a disc shaped dish part disposed between the main blade and the auxiliary blade. The dish part has an annular partition part extending upward from the outer circumferential edge part of the main blade, which is disposed at a position lower than the upper end part of the partition part.

FIELD OF THE INVENTION

The present invention relates to a drain pump, and an air conditionerprovided therewith.

BACKGROUND ART

It is known to provide a drain pump in an air conditioner in order todischarge drain water generated in a heat exchanger during coolingoperation, draining operation, and the like. Such a drain pump is builtinto a ceiling embedded type air conditioner 1 as shown in, for example,FIG. 14, FIG. 15, and FIG. 16. Here, FIG. 14 is an external perspectiveview of the air conditioner 1 (ceiling is not shown). FIG. 15 is aschematic side cross sectional view of the air conditioner 1, and is across sectional view taken along the A-A line in FIG. 16. FIG. 16 is aschematic plan cross sectional view of the air conditioner 1, and is across sectional view taken along the B-B line in FIG. 15.

The air conditioner 1 comprises a casing 2 that internally housesvarious constituent equipment, and a face panel 3 disposed on the lowerside of the casing 2. Specifically, the casing 2 of the air conditioner1 is disposed so that it is inserted in an opening formed in a ceiling Uof an air conditioned room. Furthermore, the face panel 3 is disposed sothat it is fitted into the opening of the ceiling U. Principallydisposed inside the casing 2 are: a fan 4 that sucks air inside the airconditioned room through an inlet 31 of the face panel 3 into the casing2, and blows the same out in the outer circumferential direction; and aheat exchanger 6 disposed so that it surrounds the outer circumferenceof the fan 4. In the face panel 3 are formed: an inlet 31 that sucks inthe air inside the air conditioned room; and outlets 32 that blow outthe air from inside the casing 2 into the air conditioned room.

A drain pan 7 for receiving the drain water generated in the heatexchanger 6 is disposed on the lower side of the heat exchanger 6. Thedrain pan 7 is mounted to the lower part of the casing 2. The drain pan7 comprises: an inlet 71 formed so that it communicates with the inlet31 of the face panel 3; outlets 72 formed so that they correspond to theoutlets 32 of the face panel 3; and a drain receiving groove 73 formedon the lower side of the heat exchanger 6 and that receives the drainwater. In addition, a bell mouth 5 for guiding the air sucked in fromthe inlet 31 to the impeller 41 of the fan 4 is disposed in the inlet 71of the drain pan 7. Further, a drain pump 308 that discharges the drainwater collected in the drain receiving groove 73 out of the casing 2 isdisposed in the portion of the drain receiving groove 73 of the drainpan 7 where the heat exchanger 6 is not disposed (specifically, betweenthe outlets 72). The drain pump 308 is connected via a discharge pipe(not shown) disposed outside of the casing 2.

As shown in FIG. 17, such a drain pump 308 principally comprises: a pumpcasing 81 comprising a drain inlet 81 a at the lower end part and adrain outlet 81 b at the side part; an impeller 382 disposed inside thepump casing 81 and capable of rotating about a shaft part 91 extendingin the vertical direction inside the pump casing 81; and a motor 83disposed on the upper side of the pump casing 81 and that rotationallydrives the shaft part 91 of the impeller 382. A motor fitting 89 foraffixing the drain pump 308 to the casing 2 of the air conditioner 1 ismounted on the side surface of the motor 83. Here, FIG. 17 is a sideview of the conventional drain pump 308 (depicting a cross section ofthe pump casing 81). In addition, the rotational axis line of the shaftpart 91 of the impeller 382 is the P-P line.

The pump casing 81 principally comprises: a casing main body 84comprising an opening at the upper part and disposed so that itsurrounds the sides of the impeller 382; a casing cover 85 disposed sothat it covers the opening of the upper part of the casing main body 84;and a sealing member 86 for sealing the space between the casing mainbody 84 and the casing cover 85. The casing main body 84 comprises: acylindrically shaped main body part 84 a whose diameter decreases in thedownward direction; a tubular shaped suction part 84 b comprising adrain inlet 81 a at the lower end part and extending downward from thelower end part of the main body part 84 a; and a tubular shapeddischarge nozzle part 84 c extending sideways from the drain outlet 81 bformed at the side part of the main body part 84 a. As shown in FIG. 16,one part of the discharge nozzle part 84 c passes through a side plateof the casing 2 of the air conditioner 1. The casing cover 85principally comprises an air introduction part 85 a comprising a throughhole substantially at the center that communicates with the atmosphereand the inside of the pump casing 81.

As shown in FIG. 18 and FIG. 19, the impeller 382 principally comprises:the shaft part 91 coupled to the drive shaft of the motor 83; a mainblade 392 disposed inside the main body part 84 a; an auxiliary blade 94disposed on the lower side of the main blade 392; and a disc shaped dishpart 93 disposed between the main blade 392 and the auxiliary blade 94,and having an opening 93 a comprising an annular through hole at thecenter. Here, FIG. 18 is an enlarged view that depicts the vicinity ofthe pump casing 81 of FIG. 17. FIG. 19 is a plan view of theconventional drain pump 308 (the motor 83 and the casing cover 85 arenot shown).

The shaft part 91 passes through the inside of the air introduction part85 a, and is disposed so that a gap is formed between the outercircumferential surface of the shaft part 91 and the innercircumferential surface of the air introduction part 85 a of the casingcover 85.

The main blade 392 comprises, for example: four first blades 395extending radially from the outer circumferential surface of the shaftpart 91; and four second blades 396 extending radially from the outercircumferential edge part of the opening 93 a of the dish part 93, anddisposed between the first blades 395 in the circumferential direction.The height position of the upper end part of each first blade 395(hereinafter, the height of each first blade 395 and each second blade396 from the upper end surface of the opening 93 a to the upper end partis defined as a blade height H1, as shown in FIG. 18) is the same heightfrom the inner circumferential part to the outer circumferential partthereof. In addition, the blade height H1 of the upper end part of eachsecond blade 396 from the inner circumferential part to the outercircumferential part thereof is the same height as each first blade 395.

The dish part 93 is disposed along a reduced diameter portion of themain body part 84 a, and the annular partition part 93 b extendingupward from the outer circumferential edge part thereof is disposed sothat it couples with the outer circumferential edge part of the mainblade 392. The upper end part of the partition part 93 b is disposed ata position lower than the upper end part of the main blade 392(hereinafter, the height from the upper end surface of the opening 93 ato the upper end part of the partition part 93 b of the dish part 93 isdefined as a dish height H2, as shown in FIG. 18). In other words, theupper end part of the main blade 392, viewed from the side of theimpeller 382, protrudes more on the upper side than the upper end partof the partition part 93 b. In addition, an external dimension D of thepartition part 93 b is substantially the same or slightly less than theouter diameter of the main blade 392. The auxiliary blade 94 is disposedinside the suction part 84 b, and comprises four blades extendingradially from the outer circumferential surface of the shaft part 91.

The impeller 382 of the drain pump 308 so constituted rotates in aprescribed direction when the motor 83 is driven. In so doing, a part ofthe suction part 84 b is submerged to a point lower than the watersurface of the drain water collected in the drain receiving groove 73 ofthe drain pan 7, and the drain water collected in the drain receivinggroove 73 is consequently sucked in from the drain inlet 81 a by theauxiliary blade 94, rises inside the suction part 84 b, and reaches themain body part 84 a. Further, the drain water that reaches the main bodypart 84 a is boosted by the main blade 392, and then discharged from thedrain outlet 81 b via the discharge nozzle part 84 c to the outside ofthe casing 2 of the air conditioner 1. Specifically, the drain waterdischarged from the drain outlet 81 b is discharged via the dischargepipe disposed outside of the casing 2 and connected to the dischargenozzle part 84 c. Here, the water surface that rose to the main bodypart 84 a is substantially vertically divided into parts by the dishpart 93, the flow of the drain water is partially blocked so that theflow is limited, and the drain water that contacts the main blade 392 isdischarged (e.g., refer to Patent Documents 1, 2, 3, and 4).

Moreover, the discharge flow rate can be regulated by the water level h(refer to FIG. 18), without the drain pump 308 starting and stopping. Inother words, the drain pump 308 is constituted so that the dischargeflow rate decreases if the water level h falls, and the discharge flowrate increases if the water level h rises. Further, if the water level hrises to a certain water level and reaches the maximum discharge flowrate, then the discharge flow rate will no longer change even if thewater level h rises further than that. Consequently, even if the amountof drain water generated in the heat exchanger 6 varies, stableoperation is performed with a water level that balances the amount ofdrain water generated with the discharge flow rate.

Here, as the water level h inside the main body part 84 a of the drainpump 308 falls, an air layer expands (refer to an air-liquid interface Xin FIG. 18 and FIG. 19) circularly concentric with the shaft part 91 ofthe main blade 392, which consequently decreases the effective area bywhich the main blade 392 can perform the work of supplying water, andreduces the discharge flow rate of the drain pump 308. Conversely, ifthe water level h rises, then the air layer shrinks, which consequentlyincreases the effective area by which the main blade 392 can perform thework of supplying water, and increases the discharge flow rate of thedrain pump 308. Thus, the conventional drain pump 308 is structured sothat the discharge flow rate can be regulated by the water level h.

In addition, the back pressure may decrease depending on, for example,the installation conditions (piping length, inner diameter, height,etc.) of the discharge pipe connected to the drain outlet 81 b. In sucha case, the head of the drain pump 308 decreases, which consequentlyexpands the air layer circularly concentric with the shaft part 91 ofthe main blade 392.

Compared with a pump of a type wherein an impeller is generallysubmerged completely, such a drain pump 308 is constituted so that theair-liquid interface between the air and the water is formed at aportion where the main blade 392 is disposed; consequently, the pumpefficiency is low and the operating noise is loud. Further, thisoperating noise is generated principally by the agitation of the airlayer by the main blade 392, and the air layer acceleratedly increasesthe more it expands on the outer circumferential side of the main blade392. Particularly when the head is low, the air-liquid interface betweenthe air and the water (refer to an air-liquid interface Y in FIG. 18 andFIG. 19) expands to the outer circumferential part, where thecircumferential velocity is high, which consequently generates anextremely loud operating noise. This operating noise becomes a problemparticularly if the flow rate of the fan 4 of the air conditioner 1 islow, or if the inside of the air conditioned room is quiet.

In contrast, with the aim of reducing the operating noise by making theair-liquid interface Y above the upper end part of the partition part 93b flow smoothly, it is also known to employ the impeller 382 providedwith inclined parts 395 a, 396 a at the outer circumferential part ofthe main blade 392 (specifically, the first and second blades 395, 396)only at the portion on the upper side of the upper end part of thepartition part 93 b (i.e., the portion between the blade height H1 andthe dish height H2), as shown in FIG. 20; however, even in this case,the operating noise cannot be sufficiently reduced.

Patent Document 1

Japanese Published Patent Application No. H10-115294

Patent Document 2

Japanese Published Patent Application No. 2000-80996

Patent Document 3

Japanese Published Patent Application No. 2000-240581

Patent Document 4

Japanese Published Patent Application No. 2001-342984

DISCLOSURE OF THE INVENTION

It is an object of the present invention to reduce the operating noiseof a drain pump when the head is low.

A drain pump according to the first invention comprises a casing and animpeller. The casing comprises: a drain inlet for sucking in drain waterat a lower end part; and a drain outlet for discharging drain water at aside part. The impeller comprises: a shaft part disposed inside thecasing so that it extends in the vertical direction; a main bladedisposed on the outer circumferential side of the shaft part; anauxiliary blade disposed on the lower side of the main blade; and a discshaped dish part disposed between the main blade and the auxiliary bladeand comprising an opening in the center. The dish part further comprisesan annular partition part extending upward from the outercircumferential edge part thereof. The outer circumferential edge partof the main blade is disposed at a position lower than the upper endpart of the partition part.

With this drain pump, the outer circumferential edge part of the mainblade, where the circumferential velocity is high, is disposed at aposition lower than the upper end part of the partition part;consequently, even if the air-liquid interface between the air and thewater expands to the outer circumferential part, where thecircumferential velocity is high, when the head is low, the collisionbetween the air-liquid interface and the outer circumferential part ofthe main blade can be softened, and the operating noise can be reduced.The operating noise can be reduced effectively particularly if anoperating condition of low head overlaps an operating condition of lowwater level.

Moreover, because the portion disposed at a position lower than theupper end part of the partition part is the outer circumferential edgepart of the main blade, which has a high circumferential velocity andsignificantly affects operating noise, it reduces the effect ofsoftening the collision between the air-liquid interface and the mainblade for the inner circumferential part of the main blade, which has acomparatively small effect on operating noise, while softening thecollision between the air-liquid interface and the main blade in thevicinity of the outer circumferential edge part of the main blade, andensures an effective area by which the main blade can perform the workof supplying water, which enables a drop in performance of the drainpump to be suppressed as much as possible.

Thereby, with this drain pump, the operating noise can be reduced whenthe head is low while suppressing a drop in the pump performance.

A drain pump according to the second invention is the drain pumpaccording to the first invention, wherein the outer circumferential edgepart of the main blade is disposed on the inner circumferential side ofthe inner circumferential surface of the partition part.

With this drain pump, the outer circumferential edge part of the mainblade is disposed on the inner circumferential side of the innercircumferential surface of the partition part of the dish part, and thediameter of the main blade is less than the diameter of innercircumferential surface of the dish part; consequently, it is possibleto enhance the effect of softening the collision between the air-liquidinterface and the main blade at the outer circumferential edge part ofthe main blade.

A drain pump according to the third invention is the drain pumpaccording to the first invention or the second invention, wherein theouter circumferential part of the main blade is inclined so that a bladeheight decreases toward the outer circumferential edge part.

With this drain pump, the main blade is formed so that the blade heightof the outer circumferential part of the main blade decreases toward theouter circumferential edge part, and it is easier to further ensure aneffective area at the outer circumferential part of the main blade bywhich the main blade can perform the work of supplying water;consequently, it is possible to further suppress a drop in theperformance of the drain pump.

A drain pump according to the fourth invention comprises a casing and animpeller. The casing comprises: a drain inlet for sucking in drain waterat a lower end part; and a drain outlet for discharging drain water at aside part. The impeller comprises: a shaft part disposed inside thecasing so that it extends in the vertical direction; a main bladedisposed on the outer circumferential side of the shaft part; anauxiliary blade disposed on the lower side of the main blade; and a discshaped dish part disposed between the main blade and the auxiliary bladeand comprising an opening in the center. The main blade is formed sothat the blade height decreases from the inner circumferential edge parttoward the outer circumferential edge part thereof.

With this drain pump, the blade height of the main blade decreases fromthe inner circumferential edge part toward the outer circumferentialedge part; consequently, it is possible to soften the collision betweenthe air-liquid interface and the main blade in any of these cases: thecase where, when the head is low, the air-liquid interface between theair and the water expands to the outer circumferential part, where thecircumferential velocity is high; and the case where, when the head islow, the air-liquid interface is positioned at the inner circumferentialpart, more so in the case when the water level is rising than when thewater level is low.

Thereby, with this drain pump, the operating noise can be reduced whenthe head is low, even if the position of the air-liquid interface variesdue to variations in the water level.

A drain pump according to the fifth invention comprises a casing and animpeller. The casing comprises: a drain inlet for sucking in drain waterat a lower end part; and a drain outlet for discharging drain water at aside part. The impeller comprises: a shaft part disposed inside thecasing so that it extends in the vertical direction; a main bladedisposed on the outer circumferential side of the shaft part; anauxiliary blade disposed on the lower side of the main blade; and a discshaped dish part disposed between the main blade and the auxiliary bladeand comprising an opening in the center. The jagged part, wherein theblade height varies with the jagged shape, is formed at at least theouter circumferential part of the main blade.

With this drain pump, a jagged part is formed at the outercircumferential part of the main blade, where the circumferentialvelocity is high; consequently, even if, when the head is low, theair-liquid interface between the air and the water expands to the outercircumferential part where the circumferential velocity is high, thecollision between the air-liquid interface and the outer circumferentialpart of the main blade can be softened, and the operating noise can bereduced. The operating noise can be reduced effectively particularly ifthe operating condition of low head overlaps the operating condition oflow water level.

Moreover, if the jagged part is formed also at the inner circumferentialpart of the main blade, the collision between the air-liquid interfaceand the main blade can be softened in any one of these cases: the casewhere, when the head is low, the air-liquid interface between the airand the water expands to the outer circumferential part, where thecircumferential velocity is high; and the case where, when the head islow, the air-liquid interface is positioned at the inner circumferentialpart, more so in the case when the water level is rising than when thewater level is low.

Thereby, with this drain pump, the operating noise can be reduced whenthe head is low, even if the position of the air-liquid interface variesdue to variations in the water level.

An air conditioner according to the sixth invention comprises: a heatexchanger; a drain pan for collecting drain water generated by the heatexchanger; and a drain pump as recited in any one invention of the firstinvention through the fifth invention that discharges the drain watercollected in the drain pan.

With this air conditioner, the noise of the entire air conditioner canbe reduced because the drain pump whose operating noise is low when thehead is low is used to discharge the drain water collected in the drainpan.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is an enlarged view that depicts the vicinity of a pump casing ofa drain pump according to the first embodiment of the present invention.

FIG. 2 is a plan view of the drain pump (the motor and the casing coverare not shown) according to the first embodiment of the presentinvention.

FIG. 3 graphs the actual measured values of the operating noise, undervarious water level and head conditions, with the drain pump unmounted.

FIG. 4 graphs the actual measured values of the head under variousrotational speeds.

FIG. 5 is an enlarged view that depicts the vicinity of the pump casingof the drain pump according to the second embodiment of the presentinvention.

FIG. 6 is a plan view of the drain pump (the motor and the casing coverare not shown) according to the second embodiment of the presentinvention.

FIG. 7 is an enlarged view that depicts the vicinity of the pump casingof the drain pump according to the third embodiment of the presentinvention.

FIG. 8 is a plan view of the drain pump (the motor and the casing coverare not shown) according to the third embodiment of the presentinvention.

FIG. 9 is a side view of an impeller of the drain pump according toanother embodiment of the present invention.

FIG. 10 is a side view of the impeller of the drain pump according toanother embodiment of the present invention.

FIG. 11 is a side view of the impeller of the drain pump according toanother embodiment of the present invention.

FIG. 12 is a side view of the impeller of the drain pump according toanother embodiment of the present invention.

FIG. 13 is a side view of the impeller of the drain pump according toanother embodiment of the present invention.

FIG. 14 is an external perspective view of a ceiling embedded type airconditioner.

FIG. 15 is a schematic side cross sectional view of the ceiling embeddedtype air conditioner, and is a cross sectional view taken along the A-Aline in FIG. 16.

FIG. 16 is a schematic plan cross sectional view of the ceiling embeddedtype air conditioner, and is a cross sectional view taken along the B-Bline in FIG. 15.

FIG. 17 is a side view of a conventional drain pump (depicting a crosssection of the pump casing).

FIG. 18 is an enlarged view that depicts the vicinity of the pump casingin FIG. 17.

FIG. 19 is a plan view of a conventional drain pump (the motor and thecasing cover are not shown).

FIG. 20 is a side view of the impeller of the drain pump according toanother conventional example.

EXPLANATION OF SYMBOLS

-   1 Air conditioner-   6 Heat exchanger-   7 Drain pan-   8, 108, 208 Drain pump-   81 Pump casing (casing)-   81 a Drain inlet-   81 b Drain outlet-   82, 182, 282 Impeller-   91 Shaft part-   92, 192, 292 Main blade-   93 Dish part-   93 a Opening part (opening)-   93 b Partition part-   94 Auxiliary blade-   H1 Blade height-   H2 Dish height

PREFERRED EMBODIMENTS

The following explains the embodiments of a drain pump and an airconditioner provided therewith according to the present invention,referencing the drawings.

First Embodiment

(1) Constitution and Operation of the Drain Pump

FIG. 1 and FIG. 2 depict a drain pump 8 according to the firstembodiment of the present invention used in an air conditioner 1 (referto FIG. 14 through FIG. 16), and the like. Here, FIG. 1 is an enlargedview that depicts the vicinity of a pump casing 81 of the drain pump 8according to the first embodiment of the present invention. FIG. 2 is aplan view of the drain pump 8 (a motor 83 and a casing cover 85 are notshown) according to the first embodiment of the present invention.Furthermore, excepting an impeller 82, the explanation of the drain pump8 is abbreviated because its constitution is the same as that of theconventional drain pump 308.

The impeller 82 principally comprises: a shaft part 91 coupled to adrive shaft of the motor 83; a main blade 92 disposed inside a main bodypart 84 a of the pump casing 81; an auxiliary blade 94 disposed on thelower side of the main blade 92; and a disc shaped dish part 93 disposedbetween the main blade 92 and the auxiliary blade 94, and having anopening 93 a comprising an annular through hole in the center. Here,excepting the main blade 92, the explanation of the impeller 82 isabbreviated because its constitution is the same as a conventionalimpeller 382.

The main blade 92 comprises, for example: four first blades 95 extendingradially from the outer circumferential surface of the shaft part 91;and four second blades 96 extending radially from the outercircumferential edge part of the opening 93 a of the dish part 93, anddisposed between the first blades 95 in the circumferential direction.Furthermore, the number of first blades 95 and second blades 96 thatconstitute the main blade 92 is not limited to the abovementionednumber, and various numbers thereof can be chosen.

The height position of the upper end part of each first blade 95(hereinafter, the height of each first blade 95 and each second blade 96from the upper end surface of the opening 93 a is defined as a bladeheight H1, as shown in FIG. 1) is the same height from the innercircumferential part to the outer circumferential part thereof,excepting an inclined part 95 a formed at the outer circumferentialpart. In addition, the blade height H1 of the upper end part of eachsecond blade 96 from the inner circumferential part to the outercircumferential part thereof is the same height as each first blade 95,excepting an inclined part 96 a formed at the outer circumferentialpart. Moreover, the same as a main blade 392 of the conventional drainpump 308, the portion excluding the inclined part 96 a of the main blade92 protrudes more on the upper side than the upper end part of apartition part 93 b (specifically, a dish height H2) when viewed fromthe side surface of the impeller 82.

Furthermore, the inclined parts 95 a, 96 a are formed so that one partof the outer circumferential part of each first blade 95 and each secondblade 96 is notched, and are shaped inclined so that the blade height H1shortens toward the outer circumferential edge part. In addition, theouter circumferential edge part of each of the inclined parts 95 a, 96 ais disposed at a position lower than the upper end part of the partitionpart 93 b.

In addition, the inclined parts 95 a, 96 a are notched so that the outerdiameter of each first blade 95 and each second blade 96 is shorter thanan external dimension D of the partition part 93 b, and further isshorter than a diameter d of the inner circumferential surface of thepartition part 93 b. Consequently, the outer circumferential edge partof each first blade 95 and each second blade 96 is disposed on the innercircumferential side of the inner circumferential surface of thepartition part 93 b. Furthermore, each of the inclined parts 95 a, 96 amay be shaped linearly inclined, as shown in FIG. 1, and may be shapedinclined so that it describes a curved surface.

With a drain pump 8 having a main blade 92 wherein such inclined parts95 a, 96 a are formed, the air layer expands circularly concentric withthe shaft part 91 of the main blade 92 as the water level h falls, thesame as the inside of the main body part 84 a of a conventional drainpump 308. Particularly when the head is low, the air-liquid interfacebetween the air and the water (refer to an air-liquid interface Y inFIG. 1 and FIG. 2) expands to the outer circumferential part where thecircumferential velocity is high.

However, with the drain pump 8, the outer circumferential edge part ofthe main blade 92 is disposed at a position lower than the upper endpart of the partition part 93 b by the forming of the inclined parts 95a, 96 a at the outer circumferential part of the main blade 92, whichcan soften the collision between the air-liquid interface Y and theouter circumferential part of the main blade 92, and it is consequentlypossible to reduce the operating noise generated by the agitation of theair layer by the main blade 92.

Moreover, because the portion disposed at a position lower than theupper end part of the partition part 93 b is the outer circumferentialedge part of the main blade 92, which has a high circumferentialvelocity and greatly affects operating noise: it decreases the effect ofsoftening the collision between the air-liquid interface and the mainblade for the inner circumferential part of the main blade 92, which hasa comparatively small effect on operating noise, while softening thecollision between the air-liquid interface Y and the main blade in thevicinity of the outer circumferential edge part of the main blade 92;and it ensures an effective area by which the main blade 92 can do thework of supplying water. Thereby, a decrease in the discharge flow rateof the drain pump 8 is suppressed, and a drop in pump performance can bekept to a minimum.

In addition, with the drain pump 8, the outer circumferential edge partof the main blade 92 is disposed on the inner circumferential side ofthe inner circumferential surface of the partition part 93 b of the dishpart 93, and it is consequently possible to obtain the effect ofreliably softening the collision between the air-liquid interface Y andthe main blade 92 at the outer circumferential edge part of the mainblade 92.

Furthermore, with the drain pump 8, the main blade 92 is formed so thatthe blade height H1 of the outer circumferential part of the main blade92 decreases toward the outer circumferential edge part, which makes iteasier to ensure an effective area at the outer circumferential part ofthe main blade 92 by which the main blade 92 can perform the work ofsupplying water, and it is consequently possible to further suppress adrop in the pump performance of the drain pump 8.

Thus, with this drain pump 8, a drop in the pump performance can besuppressed and the operating noise can be reduced when the head is low.In addition, because such a drain pump 8 having a low operating noisewhen the head is low is used to discharge the drain water collected in adrain pan 7 of the air conditioner 1, it becomes possible to reduce thenoise of the entire air conditioner 1, and problems such as theoperating noise of the drain pump becoming a disturbance tend not tooccur in cases such as when the flow rate of a fan 4 of the airconditioner 1 is low, or when the interior of the air conditioned roomis quiet.

(2) Examples of Experiments

The following explains the experimental results obtained for the drainpump 8 comprising a main blade 92 having the inclined parts 95 a, 96 aof the present embodiment, and a drain pump 308 comprising aconventional main blade 392, wherein actual measurements were taken ofthe operating noise with the drain pump unmounted, and of the head,which is one measure of pump performance. Here, FIG. 3 graphs the actualmeasured values of the operating noise for an unmounted drain pump undervarious water level and head conditions. FIG. 4 graphs the actualmeasured values of the head at various rotational speeds. In addition,two drain pumps were prepared as conventional drain pumps: a drain pumpcomprising a main blade not having an inclined part, as shown in FIG. 18(hereinafter, referred to as the conventional example 1); and a drainpump comprising a main blade having inclined parts 395 a, 396 a formedonly at the portion more on the upper side than the upper end part ofthe partition part 93 b shown in FIG. 20 (hereinafter, referred to asthe conventional example 2); and actual measurements of the operatingnoise and the head were conducted.

With the drain pump of the conventional example 1, as shown in FIG. 3,the operating noise is greatest (approximately 46 dBA) when the waterlevel and the head are low, the operating noise decreases toapproximately 43 dBA when the water level is high and the head is low,and the operating noise trends downward to about 30 dBA as the headincreases. In addition, as shown in FIG. 4, the head trends upward asthe rotational speed increases. In addition, with the drain pump of theconventional example 2, as shown in FIG. 3, the operating noise is lowerthan the conventional example 1 when the water level and the head arelow, but the operating noise is greatest (approximately 42 dBA) when thewater level and the head are low, the operating noise decreases toapproximately 40 dBA when the water level is high and the head is low,and the operating noise trends downward to about 30 dBA as the headincreases.

However, with the drain pump 8 of the present embodiment, as shown inFIG. 3, the operating noise is less than the operating noise of thedrain pumps of the conventional examples 1 and 2 (approximately 32 dBA)when the water level and the head are low, the operating noise increasesto approximately 37 dBA when the water level is high and the head is low(however, less than the operating noise of the drain pumps of theconventional examples 1 and 2 under the same conditions), and theoperating noise trends downward to about 30 dBA as the head increases.In addition, as shown in FIG. 4, the head becomes slightly less than thehead of the drain pump of the conventional example 1, but trends upwardas the rotational speed increases.

Here, it is considered that the operating noise when the water level andthe head are low is less than the operating noise of the drain pump ofthe conventional example 1 because the inclined parts 95 a, 96 a areformed at the outer circumferential part of the main blade 92, asdiscussed above. Moreover, it is less than the operating noise of thedrain pump of the conventional example 2 because of the difference ofthe shapes of the inclined parts 95 a, 96 a formed in the main blade 92of the drain pump 8 of the present embodiment and the inclined partsformed in the main blade of the drain pump of the conventional example2. Specifically, this is attributable to the fact that the outercircumferential edge part of each of the inclined parts 95 a, 96 aformed in the main blade 92 of the drain pump 8 of the presentembodiment is disposed at a position lower than the upper end part ofthe partition part 93 b, while the inclined parts 395 a, 396 a formed inthe main blade of the drain pump of the conventional example 2 areformed only in the portion more on the upper side than the upper endpart of the partition part 93 b. Moreover, with the drain pump 8 of thepresent embodiment, the outer circumferential edge part of the mainblade 92 is disposed on the inner circumferential side of the innercircumferential surface of the partition part 93 b of the dish part 93,and it is supposed that this consequently enhances the effect ofsoftening the collision between the air-liquid interface Y and the mainblade 92 at the outer circumferential edge part of the main blade 92. Inaddition, it is considered that the increase in the operating noise whenthe water level is high and the head is low is attributable to the factthat the inner circumferential part of the main blade 92 is the sameshape as the main blade 392 of the drain pumps of the conventionalexample 1 and the conventional example 2.

Forming the inclined parts 95 a, 96 a in the main blade 92 slightlyreduces the effective area by which the main blade 92 can perform thework of supplying water, but an effective area of the innercircumferential part of the main blade 92 is ensured; consequently, thedecrease in the head is kept to a level wherein the head becomesslightly less than the head of the drain pump of the conventionalexample 1, and a drop in the pump performance of the drain pump 8 issuppressed as much as possible.

Thus, by disposing the outer circumferential edge part of the main blade92 at a position lower than the upper end part of the partition part 93b as in the drain pump 8 of the present embodiment, a drop in the pumpperformance is suppressed, and the effect was confirmed that theoperating noise can be effectively reduced at times of low head, andparticularly when a low head operating condition overlaps with a lowwater level operating condition.

Second Embodiment

(1) Constitution and Operation of the Drain Pump

FIG. 5 and FIG. 6 depict a drain pump 108 according to the secondembodiment of the present invention used in an air conditioner 1 (referto FIG. 14 through FIG. 16), and the like. Here, FIG. 5 is an enlargedview that depicts the vicinity of the pump casing 81 of the drain pump108 according to the second embodiment of the present invention. FIG. 6is a plan view of the drain pump 108 (the motor 83 and the casing cover85 are not shown) according to the second embodiment of the presentinvention. Furthermore, excepting an impeller 182, the explanation ofthe drain pump 108 is abbreviated because its constitution is the sameas that of the conventional drain pump 308.

The impeller 182 principally comprises: the shaft part 91 coupled to thedrive shaft of the motor 83; a main blade 192 disposed inside the mainbody part 84 a of the pump casing 81; an auxiliary blade 94 disposed onthe lower side of the main blade 192; and the disc shaped dish part 93disposed between the main blade 192 and the auxiliary blade 94, andhaving an opening 93 a comprising an annular through hole in the center.Here, excepting the main blade 192, the explanation of the impeller 182is abbreviated because its constitution is the same as the conventionalimpeller 382.

The main blade 192 comprises, for example: four first blades 195extending radially from the outer circumferential surface of the shaftpart 91; and four second blades 196 extending radially from the outercircumferential edge part of the opening 93 a of the dish part 93, anddisposed between the first blades 195 in the circumferential direction.Furthermore, the number of first blades 195 and second blades 196 thatconstitute the main blade 192 is not limited to the abovementionednumber, and various numbers thereof can be chosen.

Each first blade 195 is formed so that the height position of the upperend part of the first blade 195 (hereinafter, as shown in FIG. 5, theheight of each first blade 195 and each second blade 196 from the upperend surface of the opening 93 a is defined as the blade height H1)decreases from the inner circumferential edge part to the outercircumferential edge part thereof (specifically, the upper end part ofthe outer circumferential edge part of the partition part 93 b). Inother words, the inclined part 195 a formed only at the outercircumferential part of each first blade 95 of the first embodiment isformed over each entire first blade 195. In addition, an inclined part196 a is formed so that the blade height H1 of the upper end part ofeach second blade 196 decreases from the inner circumferential edge parttoward the outer circumferential edge part thereof, the same as eachfirst blade 195. In other words, the inclined part 196 a formed only atthe outer circumferential part of each second blade 96 of the firstembodiment is formed over each entire second blade 196. Furthermore, theouter circumferential edge part of each first blade 195 and each secondblade 196 is disposed at the same height position as the upper end partof the partition part 93 b (specifically, the dish height H2), and theouter circumferential edge part of each first blade 195 and each secondblade 196 is not disposed at a position lower than the upper end part ofthe partition part 93 b, the same as the inclined parts 95 a, 96 a ofthe first embodiment. Furthermore, because these inclined parts 195 a,196 a are formed across the main blade 192 from the innercircumferential edge part to the outer circumferential edge part(specifically, from the outer circumferential surface of the shaft part91 to the outer circumferential edge part of the partition part 93 b),its inclination is gradual compared with the inclined parts 95 a, 96 aof the first embodiment. Thus, the blade height H1 of each first blade195 and each second blade 196 is less at the outer circumferential partthan at the inner circumferential part. Furthermore, each of theinclined parts 195 a, 196 a may be shaped linearly inclined, as shown inFIG. 5, and may be shaped inclined so that it describes a curvedsurface.

With a drain pump 108 having a main blade 192 wherein such inclinedparts 195 a, 196 a are formed, the air layer expands circularlyconcentric with the shaft part 91 of the main blade 192 as the waterlevel h falls, the same as the inside of the main body part 84 a of theconventional drain pump 308. Particularly when the head is low, theair-liquid interface between the air and the water (refer to anair-liquid interface Y in FIG. 5 and FIG. 6) expands to the outercircumferential part where the circumferential velocity is high.

However, with the drain pump 108, by forming the inclined parts 195 a,196 a over the entire main blade 192, the blade height H1 is lower atthe outer circumferential part than at the inner circumferential part,which can soften the collision between the air-liquid interface Y andthe outer circumferential part of the main blade 192, and it isconsequently possible to reduce the operating noise generated by theagitation of the air layer by the main blade 192.

Moreover, as the water level h rises, the air layer shrinks (refer to anair-liquid interface X in FIG. 5 and FIG. 6); however, even in thiscase, the inclined parts 195 a, 196 a formed over the entire main blade192 can soften the collision between the air-liquid interface X and themain blade 192, and the operating noise generated by the main blade 192agitating the air layer can be reduced.

Thus, with this drain pump 108, it is possible to soften the collisionbetween the air-liquid interface and the main blade 192 in any of thesecases: the case where, when the head is low, the air-liquid interfacebetween the air and the water expands to the outer circumferential part,where the circumferential velocity is high; and the case where, when thehead is low, the air-liquid interface is positioned at the innercircumferential part, more so in the case when the water level is risingthan when the water level is low; consequently, the operating noise canbe reduced when the head is low even when the position of the air-liquidinterface varies due to variations in the water level. In addition,because such a drain pump 108 having a low operating noise when the headis low is used to discharge the drain water collected in the drain pan 7of the air conditioner 1, it becomes possible to reduce the noise of theentire air conditioner 1, and problems such as the operating noise ofthe drain pump becoming a disturbance tend not to occur in cases such aswhen the flow rate of the fan 4 of the air conditioner 1 is low, or whenthe interior of the air conditioned room is quiet.

(2) Examples of Experiments

The following explains, referencing FIG. 3 and FIG. 4, the experimentalresults obtained for the drain pump 108 comprising the main blade 192having the inclined parts 195 a, 196 a of the present embodiment, andthe drain pump 308 comprising the conventional main blade 392, whereinactual measurements were taken of the operating noise with the drainpump unmounted, and of the head, which is one measure of pumpperformance.

With the drain pump 108 of the present embodiment, as shown in FIG. 3,the operating noise is less than the operating noise of the drain pumpof the conventional examples 1 and 2 (approximately 36 dBA; however,larger than the operating noise of the drain pump 8 of the firstembodiment under the same conditions) when the water level and the headare low, the operating noise decreases to approximately 35 dBA(moreover, less than the operating noise of the drain pump 8 of thefirst embodiment under the same conditions) when the water level is highand the head is low, and, further, the operating noise trends downwardto about 30 dBA as the head increases. In addition, as shown in FIG. 4,the head decreases to a point slightly less than the head of the drainpump of the conventional example 1 (however, on par with the head of thedrain pump 8 of the first embodiment), but trends upward as therotational speed increases.

Here, it is considered that the operating noise when the water level andthe head are low is less than the operating noise of the drain pump ofthe conventional example 1 because the inclined parts 195 a, 196 a areformed at the outer circumferential part of the main blade 192, asdiscussed above. In addition, it is considered that the operating noiseis greater than the operating noise of the drain pump 8 of the firstembodiment because: the inclination of the inclined parts 195 a, 196 ais gentler than the inclination of the inclined parts 95 a, 96 a of thefirst embodiment; the outer circumferential edge part of the main blade192 is not disposed at a position lower than the upper end part of thepartition part 93 b; and the effect of softening the collision betweenthe air-liquid interface and the main blade 192 at the outercircumferential part of the main blade 192 is somewhat less than that ofthe inclined parts 95 a, 96 a of the first embodiment. In addition, itis considered that the operating noise is lower than the operating noiseof the drain pump of the conventional example 2 when the water level andthe head are low because the inclined parts 195 a, 196 a are formed notonly at the outer circumferential part of the main blade 192, but overthe entire main blade 192. Furthermore, it is considered that theoperating noise is reduced when the water level is high and the head islow because: the inclined parts 195 a, 196 a are formed over the entiremain blade 92; and the effect of softening the collision between theair-liquid interface and the main blade 192 at the inner circumferentialpart of the main blade 192 is obtained, unlike the main blade of thedrain pump of the conventional examples 1 and 2, and unlike the mainblade 92 of the drain pump 8 of the first embodiment.

Forming the inclined parts 195 a, 196 a in the main blade 192 slightlyreduces the effective area by which the main blade 192 can perform thework of supplying water, but, as a result of forming the inclined parts195 a, 196 a over the entire main blade 92, an effective area of theouter circumferential part of the main blade 192 is ensured;consequently, on par with the drain pump 8 of the first embodiment, thedecrease in the head is kept to a level wherein the head becomesslightly less than the head of the drain pump of the conventionalexample 1, and a drop in the pump performance of the drain pump 108 issuppressed as much as possible.

Thus, by forming the inclined parts 195 a, 196 a over the entire mainblade 192 as in the drain pump 108 of the present embodiment, a drop inthe pump performance is suppressed, the effect wherein the operatingnoise can be reduced not only when the head and the water level are low,but also when the head is low and the water level is high, wasconfirmed; as a result, it was seen that the effect of reducingvariations in the operating noise due to variations in the head andwater level was obtained.

Third Embodiment

(1) Constitution and Operation of the Drain Pump

FIG. 7 and FIG. 8 depict a drain pump 208 according to the thirdembodiment of the present invention used in an air conditioner 1 (referto FIG. 14 through FIG. 16), and the like. Here, FIG. 7 is an enlargedview that depicts the vicinity of the pump casing 81 of the drain pump208 according to the third embodiment of the present invention. FIG. 8is a plan view of the drain pump 208 (the motor 83 and the casing cover85 are not shown) according to the third embodiment of the presentinvention. Furthermore, excepting an impeller 282, the explanation ofthe drain pump 208 is abbreviated because its constitution is the sameas that of the conventional drain pump 308.

The impeller 282 principally comprises: the shaft part 91 coupled to thedrive shaft of the motor 83; the auxiliary blade 94 disposed on thelower side of a main blade 292; and the disc shaped dish part 93disposed between the main blade 292 and the auxiliary blade 94, andhaving the opening 93 a comprising an annular through hole in thecenter. Here, excepting the main blade 292, the explanation of theimpeller 282 is abbreviated because its constitution is the same as theconventional impeller 382.

The main blade 292 comprises, for example: four first blades 295extending radially from the outer circumferential surface of the shaftpart 91; and four second blades 296 extending radially from the outercircumferential edge part of the opening 93 a of the dish part 93, anddisposed between the first blades 295 in the circumferential direction.Furthermore, the number of first blades 295 and second blades 296 thatconstitute the main blade 292 is not limited to the abovementionednumber, and various numbers thereof can be chosen.

Because a jagged part 295 a is formed, the height position of the upperend part of each first blade 295 (hereinafter, as shown in FIG. 7, theheight of each first blade 295 and each second blade 296 from the upperend surface of the opening 93 a is defined as the blade height H1)varies with the jagged shape across each entire first blade 295 from theinner circumferential edge part to the outer circumferential edge part.In addition, because a jagged part 296 a is formed, the blade height H1of the upper end part of each second blade 296 varies with a jaggedshape across the entire second blade 296 from the inner circumferentialedge part to the outer circumferential edge part.

In the present embodiment, the jagged parts 295 a, 296 a are righttriangle waveform shaped portions, and the outermost circumferentialpart thereof (hereinafter, referred to as inclined parts 295 b, 296 b)is shaped inclined so that the blade height H1 decreases toward theouter circumferential edge part. These inclined parts 295 b, 296 b areformed so that one part of the outer circumferential part of each firstblade 295 and each second blade 296 is notched, and the outercircumferential edge part thereof is disposed at a position lower thanthe upper end part of the partition part 93 b (specifically, the dishheight H2).

In addition, the inclined parts 295 b, 296 b are notched so that theouter diameter of each first blade 295 and each second blade 296 isshorter than an external dimension D of the partition part 93 b, andfurther is shorter than a diameter d of the inner circumferentialsurface of the partition part 93 b. Consequently, the outercircumferential edge part of each first blade 295 and each second blade296 is disposed on the inner circumferential side of the innercircumferential surface of the partition part 93 b. Furthermore, theshape of the jagged parts 295 a, 296 a is not limited to those in thepresent embodiment, and other shapes, such as a rectangular waveformshape and a sine waveform shape, are also applicable.

With a drain pump 208 provided with a main blade 292 wherein jaggedparts 295 a, 296 a having such inclined parts 295 b, 296 b are formed,the air layer expands circularly concentric with the shaft part 91 ofthe main blade 292 as the water level h falls, the same as the inside ofthe main body part 84 a of the conventional drain pump 308. Particularlywhen the head is low, the air-liquid interface between the air and thewater (refer to an air-liquid interface Y in FIG. 7 and FIG. 8) expandsto the outer circumferential part where the circumferential velocity ishigh.

However, with the drain pump 208, the outer circumferential edge part ofthe main blade 292 is disposed at a position lower than the upper endpart of the partition part 93 b by the forming of the jagged parts 295a, 296 a (specifically, the inclined parts 295 b, 296 b) at the outercircumferential part of the main blade 292, which can soften thecollision between the air-liquid interface Y and the outercircumferential part of the main blade 292, and it is consequentlypossible to reduce the operating noise generated by the agitation of theair layer by the main blade 292, the same as the drain pump 8 as thefirst embodiment.

Moreover, as the water level h rises, the air layer shrinks (refer tothe air-liquid interface X in FIG. 7 and FIG. 8); however, even at thistime, if the jagged parts 295 a, 296 a are formed over the entire mainblade 292, as in the present embodiment, then the jagged parts 295 a,296 a can soften the collision between the air-liquid interface X andthe main blade 292, the same as the drain pump 108 of the secondembodiment, and it is possible to reduce the operating noise generatedby the main blade 292 agitating the air layer.

Furthermore, because such a drain pump 208 having a low operating noisewhen the head is low is used to discharge the drain water collected inthe drain pan 7 of the air conditioner 1, it becomes possible to reducethe noise of the entire air conditioner 1, and problems such as theoperating noise of the drain pump becoming a disturbance tend not tooccur in cases such as when the flow rate of the fan 4 of the airconditioner 1 is low, or when the interior of the air conditioned roomis quiet.

Other Embodiments

The above explained embodiments of the present invention based on thedrawings, but the specific constitution is not limited to theseembodiments, and it is understood that variations and modifications maybe effected without departing from the spirit and scope of theinvention.

(1) Modified Example of the First Embodiment

With the main blade 92 that constitutes the impeller 82 of the drainpump 8 of the first embodiment, the outer circumferential edge part ofeach first blade 95 and each second blade 96 is disposed on the innercircumferential side of the inner circumferential surface of thepartition part 93 b due to the notching so that the inclined parts 95 a,96 a are shorter than the diameter d of the inner circumferentialsurface of the partition part 93 b; however, as shown in FIG. 9, theouter circumferential edge part of each of the inclined parts 95 a, 96 amay be formed so that it comes in contact with the inner circumferentialsurface of the partition part 93 b.

Even in this case, because the outer circumferential edge part of eachfirst blade 95 and each second blade 96 is disposed at a position lowerthan the upper end part of the partition part 93 b, it is supposed thatthe operating noise when the head is low can be reduced more than thedrain pumps of the conventional examples 1 and 2.

In addition, with the main blade 92 that constitutes the impeller 82 ofthe drain pump 8 of the first embodiment, the inclined parts 95 a, 96 aare shaped inclined so that the blade height H1 decreases linearlytoward the circumferential edge part; however, as shown in FIG. 10, onepart of the outer circumferential part of each first blade 95 and eachsecond blade 96 may be of a shape that is notched in a polygon shape;and, as shown in FIG. 11, one part of the outer circumferential part ofeach first blade 95 and each second blade 96 may be of a shape that isstraightly notched in the vertical direction.

Even in this case, it is supposed that the operating noise when the headis low can be reduced more than the drain pumps of the conventionalexamples 1 and 2 because the outer circumferential edge part of eachfirst blade 95 and each second blade 96 is disposed at a position lowerthan the upper end part of the partition part 93 b.

(2) Modified Example of the Second Embodiment

With the main blade 192 that constitutes the impeller 182 of the drainpump 108 of the second embodiment, the inclined parts 195 a, 196 a areformed so that the blade height decreases from the inner circumferentialedge part of each first blade 195 and each second blade 196 toward theouter circumferential edge part (specifically, the upper end part of theouter circumferential edge part of the partition part 93 b), and thecollision between the air-liquid interfaces X, Y and the main blade 192over the entire main blade 192 can reliably be softened, thus reducingthe operating noise when the head is low (refer to FIG. 3); however, asshown in FIG. 12, the outer circumferential edge parts of the inclinedparts 195 a, 196 a may be disposed at a position lower than the upperend part of the partition part 93 b, the same as the inclined parts 95a, 96 a of the first embodiment, and may be notched so that the inclinedparts 195 a, 196 a become shorter than the diameter d of the innercircumferential surface of the partition part 93 b.

In this case, it is supposed that the operating noise can be furtherreduced when the head and the water level are low because the effect ofsoftening the collision between the air-liquid interface and the mainblade 92 at the outer circumferential part of the main blade 92 can beenhanced.

(3) Modified Example of the Third Embodiment

With the main blade 292 that constitutes the impeller 282 of the drainpump 208 of the third embodiment, the inclined parts 295 b, 296 b areformed by notching one part of the outer circumferential part of eachfirst blade 295 and each second blade 296 so that the outer diameter ofeach first blade 295 and each second blade 296 is shorter than theexternal dimension D of the partition part 93 b, which enables thereliable softening of the collision between the air-liquid interface Yand the main blade 292 at the outer circumferential part of the mainblade 292, thereby significantly reducing the operating noise when thehead and the water level are low (refer to FIG. 3); however, as shown inFIG. 13, one part of the outer circumferential part may be formed sothat it is notched toward the outer circumferential edge part of thepartition part 93 b, without making the outer diameter of each firstblade 295 and each second blade 296 less than the external dimension Dof the partition part 93 b.

In so doing, the effect of softening the collision between theair-liquid interface and the main blade 292 at the outer circumferentialpart of the main blade 292 decreases; nevertheless, it is supposed thatit will obtain the effect of reducing the operating noise on par withthe drain pump 108 of the second embodiment.

INDUSTRIAL FIELD OF APPLICATION

Using the present invention enables a reduction in the operating noiseof the drain pump when the head is low.

1. A drain pump, comprising: a casing including a drain inlet configuredto suck in drain water at a lower end part, and a drain outletconfigured to discharge drain water at a side part; and an impellerincluding a shaft part extending in a vertical direction within saidcasing, a main blade disposed on an outer circumferential side of saidshaft part, an auxiliary blade disposed on a lower side of said mainblade, and a disc shaped dish part disposed between said main blade andsaid auxiliary blade, said dish part including an annular partition partextending upward from an outer circumferential edge part thereof, and acentral opening, said main blade having an outer circumferential edgepart that is disposed at a position lower than an upper end part of saidpartition part.
 2. The drain pump as recited in claim 1, wherein theouter circumferential edge part of said main blade is disposed on the aninner circumferential side of an inner circumferential surface of saidpartition part.
 3. The drain pump as recited in claim 1, wherein saidmain blade has an outer circumferential edge that is inclined so that ablade height of the outer circumferential part of said main bladedecreases toward the outer circumferential edge part of said dish part.4. A drain pump, comprising: a casing including a drain inlet configuredto suck in drain water at a lower end part, and a drain outletconfigured to discharge drain water at a side part; and an impellerincluding a shaft part extending in a vertical direction within saidcasing, a main blade disposed on an outer circumferential side of saidshaft part, an auxiliary blade disposed on a lower side of said mainblades, and a disc shaped dish part disposed between said main blade andsaid auxiliary blades, said main blade being is formed so that a bladeheight of said main blade decreases from an inner circumferential edgepart toward the outer circumferential edge part thereof.
 5. A drain pumpcomprising: a casing including a drain inlet configured to suck in drainwater at a lower end part, and a drain outlet configured to dischargedrain water at a side part; and an impeller including a shaft partextending in a vertical direction within said casing, a main bladedisposed on an outer circumferential side of said shaft part, anauxiliary blade disposed on a lower side of said main blade, and a discshaped dish part disposed between said main blade, said main blade beingformed with a jagged part at least at an outer circumferential part ofsaid main blade such that a blade height of said main blade varies dueto a shape of the jagged part.
 6. An air conditioner including the drainpump of claim 1, the air conditioner comprising: a heat exchanger; and adrain pan configured to collect drain water generated by said heatexchanger, with the drain pump being arranged to discharge the drainwater collected in said drain pan.
 7. The drain pump as recited in claim2, wherein said main blade has an outer circumferential edge that isinclined so that a blade height of the outer circumferential part ofsaid main blade decreases toward the outer circumferential edge part ofsaid dish part.
 8. An air conditioner including the drain pump of claim2, the air conditioner comprising: a heat exchanger; and a drain panconfigured to collect drain water generated by said heat exchanger, withthe drain pump being-arranged to discharge the drain water collected insaid drain pan.
 9. An air conditioner including the drain pump of claim3, the air conditioner comprising: a heat exchanger; and a drain panconfigured to collect drain water generated by said heat exchanger, withthe drain pump being-arranged to discharge the drain water collected insaid drain pan.
 10. An air conditioner including the drain pump of claim4, the air conditioner comprising: a heat exchanger; and a drain panconfigured to collect drain water generated by said heat exchanger, withthe drain pump being-arranged to discharge the drain water collected insaid drain pan.
 11. An air conditioner including the drain pump of claim5, the air conditioner comprising: a heat exchanger; and a drain panconfigured to collect drain water generated by said heat exchanger, withthe drain pump being-arranged to discharge the drain water collected insaid drain pan.
 12. An air conditioner including the drain pump of claim7, the air conditioner comprising: a heat exchanger; and a drain panconfigured to collect drain water generated by said heat exchanger, withthe drain pump being-arranged to discharge the drain water collected insaid drain pan.